(1) Field of the Invention
The present invention generally relates to images. More specifically, the present invention relates to producing composite images.
(2) Description of the Related Art
The word "panorama" originates from the Greek words "pan" meaning "all" and "horama" meaning "view" or "sight". The modern day version has several meanings: 1) an unobstructed and wide view of an extensive area; 2) an extended pictorial representation; 3) a continuously passing or changing scene or unfolding of events; and 4) a comprehensive surveillance of a subject.
Composite pictures that represent unobstructed and wide views of an extensive area are typically produced by using a camera such as, by way of example, a 35 mm camera with a 15 mm lens. The camera is mounted on a tripod and a series of photographs are shot while turning the camera 360.degree. about a fixed point (center of tripod). The camera is rotated, after each exposure, at discrete angles such as, by way of example, 20 or 30 degrees.
Subsequently, the photographs may be digitized and stored onto a storage device, such as a compact disk. Then, conventional image "stitching" systems, such as, by way of non-limiting example, Quick Time VR Authoring Tools Suite, available from Apple Computer Corp., of Cupertino, Calif., map the overlapping features of successive images and stitch these images together. Stitching is a process where two or more discrete images, that are part of a larger scene, are combined, such that the combination of several discrete images represents one part of the larger image.
To stitch single images together, without distortion, it is desirable to rotate the camera about a focal point of the lens. In other words, the focal point of the lens should coincide with the center of rotation of the camera. It is also desirable to determine a field of view by measuring the focal length of the lens. Since the focal length may change with every set of pictures taken, such as in a camera equipped with a zoom mechanism, a photographer should memorize or record the focal length for each set of pictures taken and adjust the camera mount accordingly. If the camera is not rotated about the focal point of the lens used for a particular set of images, distortion may occur. Additionally, the system that stitches the resulting images together should be provided, before stitching, with the angle at which each image was generated to calculate an absolute offset between different images to be stitched. Identifying the focal length and angle, for each set of pictures taken, and adjusting the camera mount to coincide with the focal point imposes considerable overhead.
FIG. 1 diagrammatically illustrates a cross-sectional view of a camera 100, which is mounted on a tripod (not shown) having a center of rotation (CR) 114. Camera 100 includes a lens 102 having a focal point (FP) 116 and a focal length 103. Typically, an incident image of a scene to be recorded is projected onto lens 102, while camera 100 is rotated 360.degree. about its center of rotation 114. The image is focalized at focal point 116 and projected onto a photosensitive recording medium such as film 104.
Later, during the processing of a set of images obtained from film 104, conventional systems typically assume that the distance between focal point 116 and the tripod's center of rotation 114 is 0. In reality, the location of focal point 116 may not coincide with the tripod's center of rotation 114. Current processes of stitching multiple images into a composite image do not geometrically correct the distortions caused by the mismatch between the focal point 116 and the tripod center of rotation 114. While some processes automatically or manually "warp" the images' edges, these processes are costly and time-consuming or may require the expertise of a professional photographer.
Other techniques of producing a composite image record an extremely wide-angle image by using a fish eye lens, such as a lens with a 230.degree. field of view. The problem with these techniques is that the type of lenses used by these techniques are expensive and therefore not accessible to amateur photographers.
It is desirable to provide a technique for creating composite pictures with images that blend smoothly with one another and with reduced distortion. It is further desirable to provide a technique for producing composite pictures without expensive equipment or the expertise of a professional photographer.